GPSBabel supports data filtering. Data filters are
invoked from the command line via the '-x' option. It should be
noted that data filters are invoked in the internal pipeline at
the point that corresponds to their position on the
command. This implies that specifying a filter before reading
any data ('-x <filter> -f <file>'), despite being
legal, will not have any effect. The advantage is that filters
can be used intermittently between several variations of input
and output functions. It should also be noted that filtering
data from different input types can sometimes produce
undesirable results due to differences in the native data
formats.

Beware that most filters only apply to a certain kind of
data. This is usually indicated below by referring to points,
tracks or routes in the first sentence which describes each
filter or in the table at gpsbabel.org
.